Pressure regulators have existed for many years Two major species of mechanical fluid pressure regulators are common: piston-type and diaphragm-type. In general, however, these have not proven entirely satisfactory in practice.
A piston-type regulator uses a spring-biased piston in a bore to regulate output pressure with the piston always trying to reside in equilibrium. When not in equilibrium, the piston moves up or down in the bore thus opening or shutting an intake valve from a high-pressure source. One side of the piston is biased by a spring force and the other side of the piston is biased by pressurized gas.
A diaphragm-type regulator works in a very similar way. Rather than moving a piston in a bore, a diaphragm acts as a flexure, biased on one side typically by a spring. The other side of the diaphragm contains the regulated pressure. When the biasing forces on each side are not in equilibrium, the diaphragm flexes thus opening or closing an inlet valve from the high-pressure source.
Regulators that are designed to handle high source pressures, whether they be of the piston-type or diaphragm-type typically use a hard valve and seat as the major components of the inlet valve assembly. The design of a hard valve and seat works well until the smallest bit of contamination, corrosion, or surface imperfection or seal ‘set’ is introduced into the valve assembly. The result is a faulty regulator that will not predictably produce a substantially constant outlet pressure.
Likewise, a piston-type or diaphragm-type regulator designed to regulate lower source pressures typically uses a soft elastomeric seal in the valve assembly to hold back the source pressure. This art is less prone to failure due to contamination, corrosion, or surface imperfections compared to the hard valve and seat because the elastomeric seal conforms to minor valve imperfections. Unfortunately, an elastomeric seal is not capable of retaining high source pressures because the high pressures may cause permanent deformation and/or swelling. In addition, explosive decompression results when the high-pressure source is suddenly removed from an elastomeric seal sometimes causing a permanently defective seal.